Flash Memory Program Method Using Local Voltage Differentiation
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Solution Overview
Problem
Highly integrated flash memory devices face increased program disturbance due to reduced intervals between memory cells and signal lines, affecting not only selected but also unselected memory cells within the same word line and string, despite existing program-inhibit methods.
Innovation Solution
A program method for flash memory devices that applies a pass voltage to word lines to boost channel voltage, discharges the boosted voltage, and applies a local voltage lower than the pass voltage but equal to or higher than ground voltage to at least one word line adjacent to the selected word line, preventing potential differences between memory cell channels and adjacent cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If flash memory devices are highly integrated to increase storage capacity, then storage density is improved, but program disturbance increases due to reduced intervals between memory cells and signal lines
Solution Approach 1:
The patent applies different voltage levels to different word lines based on their position relative to the selected word line. Specifically, a first voltage level is applied to a first word line adjacent to the selected word line, while a second voltage level (different from the first) is applied to a second word line adjacent to the selected word line. This local differentiation of voltage levels prevents program disturbance in highly integrated flash memory devices by creating distinct electrical environments for different memory cell regions.
2Productivity
If a program voltage is applied to a selected word line to program memory cells, then programming speed is improved, but unselected memory cells on the same word line are unintentionally programmed causing program disturbance
Solution Approach 1:
The patent changes the voltage parameter applied to different word lines during the programming operation. While a high program voltage is applied to the selected word line to enable fast programming, different voltage levels (first and second voltage levels) are applied to adjacent word lines to prevent their memory cells from being unintentionally programmed. This parameter differentiation maintains both programming speed and accuracy.
3Device complexity
If the interval between memory cells and signal lines is reduced to increase integration, then device complexity is reduced, but coupling between cells increases causing program disturbance to affect more memory cells
Solution Approach 1:
The patent creates locally differentiated voltage conditions around the selected word line by applying a first voltage level to a first adjacent word line and a second voltage level to a second adjacent word line. This local quality differentiation counteracts the increased coupling effects resulting from reduced intervals between memory cells and signal lines in highly integrated devices.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents program disturbance by eliminating potential differences between memory cell channels, enhancing programming accuracy and reliability in high-integration flash memory devices.
Implementation Method 1
applying a pass voltage to word lines to boost a channel voltage
Implementation Method 2
A program operation may then be carried out with respect to selected memory cells by applying a high voltage (e.g., 20V) to a word line connected to the selected memory cells. During the program operation, threshold voltages of the selected memory cells may be shifted to a higher threshold voltage
Data Source
AI summary
A flash memory and a program method of the flash memory include applying a pass voltage to word lines to boost a channel voltage, which is discharged to a ground voltage. A program voltage is applied to a selected word line and a local voltage is applied to at least one word line supplied with the pass voltage while the program voltage is being applied to the selected word line. The local voltage is lower than the pass voltage and equal to or higher than the ground voltage. The boosted channel voltage may be discharged before the program voltage is applied to the selected word line.